The proposed research is designed to elucidate the molecular nature of the steps in the head assembly of bacteriophage P22. Emphasis is placed upon understanding the properties and biochemical mechanisms of action of the proteins involved in DNA encapsulation and cutting. Of particular interest is the product of gene 8, which acts catalytically to aid capsid assembly and acts as a type of "molecular scaffold" during assembly, and whose synthesis is apparently feedback regulated by some feature of the assembly process. The proteins will be characterized biochemically and functionally by devising in vitro assays specific for the various proteins. Simultaneously with DNA packaging the capsid is enlarged; the role of the coat protein (gene 5 product) in this process will be investigated. BIBLIOGRAPHIC REFERENCES: Lew, K. and Casjens, S. (1975) Genetic Control of Phage P22 Early Proteins. Virology 68:525-533. Earnshaw, W., Casjens, S. and Harrison, S. (1976) Molecular Structure of Bacteriophage P22 and Its Precursor Structures I: Low Angle X-Ray Diffraction Studies. J. Mol. Biol. 104: 387-410.